Block copolymer represents a very important class of polymeric materials which have been widely used as dispersants, compatibilizers, thermoplastic elastomers, adhesives, rheology modifiers, etc. Living polymerization paves the best way to prepare the block copolymers. However, since monomers usually have very strong chemoselectivity towards active centers, the block copolymerization across different mechanisms has been always difficult.
Moreover, contrary to living ionic polymerization, radical polymerization was not a well-controlled process until 1993. Therefore, synthesis of block copolymer through transformation from living ionic polymerization to living radical polymerization has not been well explored. In 1995, a living radical polymerization process named atom transfer radical polymerization (ATRP) was discovered (Wang, J. Am. Chem. Soc. 117, 5614 (995)). The most important feature of ATRP is that one may synthesize various well-defined polymers under radical polymerization conditions (Wang, Polymeric Material Science and Engineering (ACS, Polymer Materials Div.), 73, 416(1995)). Given the fact that an alkyl halide is used to initiate the ATRP, several papers reported synthesizing the block copolymers by transformation from a polymeric halide obtained from living cationic polymerization to ATRP. Coca et al first synthesized chlorine-ended styrene (PSt-CI) or .alpha., W-dichlorine polyisobutene end-capped with a few units of styrene (Cl-St-PIB-StCl) by living cationic polymerization and followed with ATRP of methyl acrylate (MA) or isobornyl acrylate (IBA) with the formation of polystyrene-b-poly methyl acrylate (PSt-b-PMB) and PMA(IBA)-b-St-PIB-St-PMA(IBA), respectively (Coca, Polymer Preprint (ACS, Polymer Chemistry Div.), 38(1), 693(1997)). A similar approach was demonstrated by Chen et al in preparing PSt-b-PIB-b-PSt block copolymers (Chen, Polymer Preprint (ACS, Polymer Chemistry Div.), 38(1), 715(1997)).